Man-made boards, such as fiberboard, can be embossed or molded to have three-dimensional shapes and various design and structural features found in natural wood. Types of useful man-made boards including: (a) fiberboards such as hardboard (e.g., low-density hardboard), soft board, and medium-density fiberboard and (b) chipboards such as particleboard, medium-density particleboard, and oriented strandboard (“OSB”). Composites of these boards are also useful. Such boards, particularly hardboard, have found widespread use in the manufacture of doorskins.
Commonly, doorskins (also referred to as door facings) are molded from a planar cellulosic mat to include one or more interior depressions or contours, such as one or more square or rectangular depressions that do not extend to the outer edge or periphery of the doorskin product. Doorskins often require inclined molded walls having a plurality of contours that include varied curved and planar surfaces. Where the depressions or contours are included on a doorskin product, this can serve to replicate a more expensive natural wood paneled door. For example, door skins having two, three, four, five, and six panel designs are commonly produced. The exterior or visible surfaces of the fiberboard also can be embossed with a design simulating a wood grain pattern such as found in a natural piece of wood.
A hollow core door typically includes a peripheral frame, and two door skins having exterior surfaces and interior surfaces secured to opposite sides of the frame using an adhesive binder. The binder is placed at least at the contact points along the periphery of the door assembly. Because the door skins are contoured, and because of the width of the frame, an open interior or hollow space of varying dimensions is formed between the spaced door skins.
A door having such an open interior may not have the characteristics of a natural solid wood door, because the interior spaces defined by the door skins will be hollow or empty. The hollow spaces cause the door to be lighter than may be preferred. Further, the sound insulation provided by such doors may not be satisfactory in particular installations. A core material (e.g., core pieces or components) is sometimes used to fill these hollow spaces. Such a door may be known as a hollow core door.
Conventional core materials for use in hollow core doors include corrugated cardboard and paper. However, such materials may not provide adequate sound insulation. In addition, they may not provide the door with the desired weight, for example the weight of a similarly-styled natural solid wood door.
Other conventional core materials include wood composite materials, such as composite softboard. Such door cores are suitable for some applications, such as doors requiring relatively thin door cores having a thickness of 0.375 inches or less. However, standard exterior residential door cores are 1.125 inches thick (for a 1.375 inch thick door). Standard exterior commercial door cores are typically 1.50 inches thick (for a 1.750 inch thick door). The manufacture of conventional door cores using prior techniques have not been cost effective for door cores having a thickness or caliper of 1.00 inch or greater.
Generally, conventional techniques for providing a thicker door core suitable for exterior residential and commercial door use involve either laminating two or more thinner boards using a synthetic resin or molding a single core. Neither of these techniques provides an inexpensive, cost effective core product for all core requirements.
Techniques involving laminating two or three relatively thin, wood composite boards using a synthetic adhesive, such as casein or polyvinyl acetate, are expensive and inefficient. The adhesive increases manufacturing costs. In some cases, manufacturing costs for producing a core component having a caliper of 1.00 inch or more have been cost prohibitive when adhesives are used. Therefore, such methods are not desirable for door core manufacturers, or result in an expensive door for consumers.
Techniques involving molding a mat of material to the desired configuration and caliper of 1.00 inch or greater also fail to provide a cost effective alternative. Many doors include a door core component having a density of between about 10 lb/ft3 to about 30 lb/ft3. When forming a one-piece core component in that density range, having a thickness of more than 1.00 inch, it is difficult to successfully dry the core material thoroughly without burning the surfaces. In addition, manufacturing costs are increased due to the amount of press time and press temperature required, as well as the amount of material needed to form the core.
Therefore, there is a need for a door core component having a thickness of 1.00 inch or greater that is cost effective to manufacture, and that has insulation and weight characteristics desirable to consumers.